Switch status detection circuit for multiple light level lighting systems

Abstract

A switch status detection circuit is provided, including three input terminals and a ground terminal. Two input terminals connect to a power supply via respective switches, receiving a respective voltage signal. The third connects to the power supply, receiving a neutral signal. A neutral synchronization circuit, between the third and the ground terminal, generates a positive pulsed current signal as a function of the neutral signal. Two capacitors, each with a respective first terminal connected to a corresponding input terminal, and a respective second terminal connected to the ground terminal, are charged by the current signal when the capacitor's corresponding switch is in an off state. Respective output terminals are coupled to each capacitor's first terminal to provide respective control signals, indicating the respective switch's state as a function of a voltage level across that capacitor. Each control signal has a logic level corresponding to its respective switch's state.

1 . A switch status detection circuit, comprising:
 a first input terminal adapted to connect to an AC power supply via a first switch and to receive a first voltage signal with respect to ground potential from the AC power supply;   a second input terminal adapted to connect to the AC power supply via a second switch and to receive a second voltage signal with respect to ground potential from the AC power supply;   a third input terminal adapted to connect to a neutral input terminal of the AC power supply and to receive a neutral voltage signal with respect to ground potential from the AC voltage supply;   a ground terminal adapted to couple to ground potential;   a neutral synchronization circuit connected between the third input terminal and the ground terminal, the neutral synchronization circuit configured to generate a positive pulsed current signal as a function of the neutral voltage signal;   a first capacitor having a first terminal and a second terminal, wherein the first terminal of the first capacitor is coupled to the first input terminal, and wherein the second terminal of the first capacitor is coupled to the ground terminal, and wherein the positive pulsed current signal charges the first capacitor when the first switch is in an off state;   a second capacitor having a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the second input terminal, and wherein the second terminal of the second capacitor is coupled to the ground terminal, and wherein the positive pulsed current signal charges the second capacitor when the second switch is in an off state;   a first output terminal coupled to the first terminal of the first capacitor to provide a first control signal that indicates a state of the first switch as a function of a voltage level across the first capacitor, the first control signal having a first logic level when the first switch is in the off state, the first control signal having a second logic level when the when the first switch is in an on state; and   a second output terminal coupled to the first terminal of the second capacitor to provide a second control signal that indicates a state of the second switch as a function of a voltage level across the second capacitor, the second control signal having a first logic level when the second switch is in the off state, the second control signal having a second logic level when the when the second switch is in an on state.   
     
     
         2 . The switch status detection circuit of  claim 1 , wherein the neutral synchronization circuit comprises:
 a resistor connected to the third input terminal;   a neutral synchronization capacitor connected in series with the resistor; and   a diode having an anode connected to the ground terminal, and a cathode connected to the neutral synchronization capacitor.   
     
     
         3 . The switch status detection circuit of  claim 2 , further comprising:
 a first transistor having a base terminal, an emitter terminal, and a collector terminal, wherein the base terminal of the first transistor is connected to the neutral synchronization capacitor, the emitter terminal of the first transistor is connected to the first input terminal via a first detection channel diode, and the collector terminal of the first transistor is connected to the emitter terminal of the first transistor via a first detection channel resistor; and   a second transistor having a base terminal, an emitter terminal, and a collector terminal, wherein the base terminal of the second transistor is connected to the neutral synchronization capacitor, the emitter terminal of the second transistor is connected to the second input terminal via a second detection channel diode, and the collector terminal of the second transistor is connected to the emitter terminal of the second transistor via a second detection channel resistor.   
     
     
         4 . The switch status detection circuit of  claim 2 , further comprising:
 a first inverter stage to generate the first control signal as a function of the voltage level across the first capacitor; and   a second inverter stage to generate the second control signal as a function of the voltage level across the second capacitor.   
     
     
         5 . The switch status detection circuit of  claim 1 , wherein the first control signal has a low logic level when the first switch is in the off state and the first control signal has a high logic level when the first switch is in the on state, and wherein the second control signal has a low logic level when the second switch is in the off state and the second control signal has a high logic level when the second switch is in the on state. 
     
     
         6 . The switch status detection circuit of  claim 1 , wherein the first output terminal is connected to a lighting system converter circuit to provide the first control signal thereto, and the second output terminal is connected to the lighting system converter circuit to provide the second control signal thereto, wherein the lighting system converter circuit provides voltage to a plurality of lamps as a function of the logic level of the first control signal and the logic level of the second control signal. 
     
     
         7 . A method implemented by a switch status detection circuit, comprising:
 receiving a first voltage signal from an alternating current (AC) power supply via a first input terminal relative to ground potential, wherein the first input terminal is connected to the AC power supply via a first switch, and wherein the first voltage signal has a phase corresponding to the state of the first switch;   receiving a second voltage signal from an AC power supply via a second input terminal relative to ground potential, wherein the second input terminal is connected to the AC power supply via a second switch, and wherein the second voltage signal has a phase corresponding to the state of the second switch;   receiving a neutral voltage signal from the AC power supply via a neutral input terminal relative to ground potential, wherein the neutral voltage signal has a phase;   generating a first direct current (DC) voltage across a first capacitor as a function of the neutral voltage signal being in-phase with the first voltage signal;   generating a second DC voltage across a second capacitor as a function of the neutral voltage signal being in-phase with the second voltage signal;   generating a first control signal as a function of the DC voltage across the first capacitor, wherein the first control signal has a logic level corresponding to the DC voltage across the first capacitor;   generating a second control signal as a function of the DC voltage across the second capacitor, wherein the second control signal has a logic level corresponding to the DC voltage across the second capacitor; and   providing the first control signal and the second control signal to an output system, wherein the output system uses the first control signal and the second control signal to operate.   
     
     
         8 . The method of  claim 7 , wherein receiving a first voltage signal comprises:
 receiving a first voltage signal from an alternating current (AC) power supply via a first input terminal relative to ground potential, wherein the first input terminal is connected to the AC power supply via a first switch, and wherein the first voltage signal has a first phase when the first switch is non-conductive, and the first voltage signal has a second phase when the first switch is conductive.   
     
     
         9 . The method of  claim 8 , wherein receiving a first voltage signal comprises:
 receiving a first voltage signal from an alternating current (AC) power supply via a first input terminal relative to ground potential, wherein the first input terminal is connected to the AC power supply via a first switch, and wherein the first voltage signal has a first phase when the first switch is non-conductive, and the first voltage signal has a second phase when the first switch is conductive, wherein the second phase differs from the first phase by one hundred and eighty degrees.   
     
     
         10 . The method of  claim 8 , wherein receiving a second voltage signal comprises:
 receiving a second voltage signal from an AC power supply via a second input terminal relative to ground potential, wherein the second input terminal is connected to the AC power supply via a second switch, and wherein the second voltage signal has a first phase when the second switch is non-conductive, and the second voltage signal has a second phase when the second switch is conductive.   
     
     
         11 . The method of  claim 10 , wherein receiving a second voltage signal comprises:
 receiving a second voltage signal from an AC power supply via a second input terminal relative to ground potential, wherein the second input terminal is connected to the AC power supply via a second switch, and wherein the second voltage signal has a first phase when the second switch is non-conductive, and the second voltage signal has a second phase when the second switch is conductive, wherein the second phase differs from the first phase by one hundred and eighty degrees.   
     
     
         12 . The method of  claim 10 , wherein receiving a neutral voltage signal comprises:
 receiving a neutral voltage signal from the AC power supply via a neutral input terminal relative to ground potential, wherein the neutral voltage signal is in-phase with the first voltage signal having the first phase and with the second voltage signal having the first phase.   
     
     
         13 . The method of  claim 7 , wherein generating a first control signal comprises:
 generating a first control signal as a function of the DC voltage across the first capacitor, wherein the first control signal has a first logic level when the first DC voltage exists across the first capacitor and otherwise has a second logic level.   
     
     
         14 . The method of  claim 13 , wherein generating a second control signal comprises:
 generating a second control signal as a function of the DC voltage across the second capacitor, wherein the second control signal has a first logic level when the second DC voltage exists across the second capacitor and otherwise has a second logic level.   
     
     
         15 . The method of  claim 14 , wherein generating a first control signal comprises:
 generating a first control signal as a function of the DC voltage across the first capacitor, wherein the first control signal has a low logic level when the first switch is in a non-conductive state, and wherein the first control signal has a high logic level when the first switch is in a conductive state;   
       and wherein generating a second control signal comprises:
 generating a second control signal as a function of the DC voltage across the second capacitor, wherein the second control signal has a low logic level when the second switch is in a non-conductive state, and wherein the second control signal has a high logic level when the second switch is in a conductive state. 
 
     
     
         16 . The method of  claim 7 , wherein providing the first control signal and the second control signal to an output system comprises:
 providing the first control signal and the second control signal to a lighting system converter circuit, wherein the lighting system converter circuit uses the first control signal and the second control signal to control a lighting level of a plurality of lamps.   
     
     
         17 . A power converter to power a plurality of lamps from an alternating current (AC) power supply, the power converter comprising:
 a first switch adapted to selectively connect the power converter to a first high voltage terminal of the AC power supply, the first switch having an on state and an off state;   a second switch adapted to selectively connect the power converter to a second high voltage terminal of the AC power supply, the second switch having an on state and an off state;   a lighting system converter circuit to provide power suitable for energizing at least one lamp in the plurality of lamps; and   a switch status detection circuit comprising:
 a first input terminal coupled to the first switch to receive a first voltage signal with respect to ground potential from the AC power supply; 
 a second input terminal coupled to the second switch to receive a second voltage signal with respect to ground potential from the AC power supply; 
 a third input terminal coupled to a neutral input terminal of the AC power supply to receive a neutral voltage signal with respect to ground potential from the AC voltage supply; 
 a ground terminal coupled to ground potential; 
 a neutral synchronization circuit connected between the third input terminal and the ground terminal, the neutral synchronization circuit configured to generate a positive pulsed current signal as a function of the neutral voltage signal; 
 a first capacitor having a first terminal and a second terminal, wherein the first terminal of the first capacitor is coupled to the first input terminal of the switch status detection circuit, and wherein the second terminal of the first capacitor is coupled to the ground terminal of the switch status detection circuit, and wherein the positive pulsed current signal charges the first capacitor when the first switch is in the off state; 
 a second capacitor having a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the second input terminal of the switch status detection circuit, and wherein the second terminal of the second capacitor is coupled to the ground terminal of the switch status detection circuit, and wherein the positive pulsed current signal charges the second capacitor when the second switch is in the off state; 
 a first output terminal coupled to the first terminal of the first capacitor and to the lighting system converter circuit to provide a first control signal to the lighting system converter circuit, wherein the first control signal indicates the state of the first switch as a function of a voltage level across the first capacitor, the first control signal having a first logic level when the first switch is in the off state, the first control signal having a second logic level when the when the first switch is in the on state; and 
 a second output terminal coupled to the first terminal of the second capacitor and to the lighting system converter circuit to provide a second control signal to the lighting system converter circuit, wherein the second control signal indicates the state of the second switch as a function of a voltage level across the second capacitor, the second control signal having a first logic level when the second switch is in the off state, the second control signal having a second logic level when the when the second switch is in the on state; 
   wherein the lighting system converter circuit receives the first control signal via the first output terminal of the switch status detection circuit and receives the second control signal via the second output terminal of the switch status detection circuit, and provides power to the plurality of lamps as a function of the logic level of the first control signal and the logic level of the second control signal.   
     
     
         18 . The power converter of  claim 17 , wherein the neutral synchronization circuit comprises:
 a resistor connected to the third input terminal;   a neutral synchronization capacitor connected in series with the resistor; and   a diode having an anode connected to the ground terminal, and a cathode connected to the neutral synchronization capacitor.   
     
     
         19 . The power converter of  claim 18 , further comprising:
 a first transistor having a base terminal, an emitter terminal, and a collector terminal, wherein the base terminal of the first transistor is connected to the neutral synchronization capacitor, the emitter terminal of the first transistor is connected to the first input terminal via a first detection channel diode, and the collector terminal of the first transistor is connected to the emitter terminal of the first transistor via a first detection channel resistor; and   a second transistor having a base terminal, an emitter terminal, and a collector terminal, wherein the base terminal of the second transistor is connected to the neutral synchronization capacitor, the emitter terminal of the second transistor is connected to the second input terminal via a second detection channel diode, and the collector terminal of the second transistor is connected to the emitter terminal of the second transistor via a second detection channel resistor.   
     
     
         20 . The power converter of  claim 18 , further comprising:
 a first inverter stage to generate the first control signal as a function of the voltage level across the first capacitor; and   a second inverter stage to generate the second control signal as a function of the voltage level across the second capacitor.